Crystal grinding device



May 30, 1950 F. G. VOLKEL CRYSTAL GRINDING DEVICE 5 Sheets-Sheet 1 Filed July 31, 1945 May 30, 1950 F. G. VOLKEL CRYSTAL GRINDING DEVICE 5 Sheets-Sheet 2 Filed July 31, 1945 INVENTOR. FRANK G. VOLKEL.

.wm mm mm ATTORNEY y 1950 F. G. VOLKEL 2,509,402

CRYSTAL GRINDING DEVICE Filed July 31, 19 45 5 Sheets-Sheet 3 INVENTOR. FRANK G. VOLKEL y 1950 F. G. VOLKEL 2,509,402

CRYSTAL GRINDING DEVICE Filed July 31, 1945 5 Sheets-Sheet 4 a 2 5'5 i v I 2 Q 0: L PM a l l I l I a ll 0 M110 6- N m 9 E 2 4m zW'IIII/l/o 5 g "3 Kw sgN 'INVENTOR. FRANK s. VOLKEL I ATTORNEY May 30, 1950 F. G. VOLKEL CRYSTAL GRINDING DEVICE 5 Sheets-Jaheet 5 Filed July 51, 1945 INVENTOR. G. VOLKEL FRANK ATTORNEY Patented May 30, 1950 CRYSTAL GRINDING DEVICE Frank G. Volkel, Los Angeles, Calif., assignor to Volkel Bros. Machine Works, Los Angeles, Calif., a copartnership Application July 31, 1945, Serial No. 608,014 6 Claims. (01. 51-124 This invention relates to machines for ac-- curately facing objects or articles and relates in particular to a grinding and polishing machine.

The invention, as disclosed herein, although it has many uses, is especially adapted for the accurate grinding of the edges of crystals which are employed in radio devices.

It is an object of the invention to provide a device capable of performing an accurate grinding of these crystals and of many other articles, including jewels and other hard materials, as well as softer materials, if desired. A further object of the invention is to provide a grinding device which is of simple and economical construction, and avoids many of the disadvantages found in grinding devices, wherein a carriage which carries the work is moved back and forth in guides or ways. In the present invention, the work carrying part is supported in radial bearings, so that it has a swinging movement instead of a straight line movement, this manner of supporting the work holding means for swinging movement cooperating with a very simple means for producing the swinging movement, and controllin the swinging movement so that the work supporting means travels slowly during the working stroke and moves rapidly during the return stroke or movement.

A further object of the invention is to provide a simple means for producing relative movement of the tool or grinding wheel and the work support so that the tool or grinding wheel and the work are progressively brought closer together as the facing operation progresses. It is a further bject of the invention to provide a feed mechanism which may be operated manually or automatically and which may be set so as to discontinue the feed at a predetermined point.

An object of the invention is to provide a del a of character herein set forth having a pie adju able feed mechanism which is incorporated 1n and Supported by the oscillating support for the work on which the facing operaperformed.

object of the invention i to provide object of the invention is to prodevice of this character having an adjuste work holder and a simple means for adangularity of the work with relation A further object of the invention is to provide a simple feed mechanism wherein the force to 2 produce the feed movement is applied through a yieldable part which will yield when the predetermined end of the feed movement or distance is reached.

It is an object of the invention to provide a device of this character having a, simple feed means in conjunction with a stop adjustable into a position determining the point at which the facing operation is to conclude, and yieldable means for gradually carrying on the feed movement until the stop is, reached, the stop then preventing feeding action.

A further object of the invention is to provide a simple means for adjusting the rate of speed, and a further object to provide a simple feeding means which accomplishes the feeding action at the end of the return stroke of the work holder, the result being that there is substantially no cutting action during the return stroke.

Further objects, features, and advantages of the invention will be brought out in the following part of the specification.

Referring to the drawings which are for illustrative purposes only,

Fig. 1 is a partly sectioned side elevation of the invention.

Fig. 2 is an enlarged fragmentary cross section taken as indicated by the line 2-2 of Fig. 3.

Fig. 3 is a rear elevational view of the upper portion of the device shown in Fi 1.

Fig. 4 is a sectional view taken as indicated by the line 44 of Fig. 2.

Fig. 5 is a sectional view taken as indicated by the line 5-5 of Fig. 2.

Fig. 6 is a front elevation of the upper portion of the device, shown to reduced scale.

Fig. "I is an enlarged fragmentary sectional view showing the work holder and the simple means for adjusting the angularity thereof.

Fig. 8 is an enlarged fragmentary elevational view of the handle and projecting stem of the angular adjusting means. This view show the indioia for indicating the adjustment.

Fig. 9 is an enlarged perspective view of the adjusting block used in the device.

Fig. 10 is an enlarged perspective view of the feed adjusting member of the device.

Fig. 11 is a cross section taken as indicated by the line H-il of Fig. 7.

Fig. 12 is an elevational view of the disc drive taken from the position indicated by the line l2- 52 of Fig. 1.

The device includes a stand or base in which is of hollow structure so that a reservoir H for ,cutting or grinding fluid or compound may be placed in its lower part with a motor driven pump I2 for circulation of the liquid. On the upper portion of the stand it there is a supporting body 53 formed so as to provide a drain pan M from which a drain pipe l5 extends downward to the reservoir 4 I. On the supporting body l3 there is mounted a casting'lfi having as a part thereof a tubular wall ll, and on this casting It a tubular spindle support i8 is secured in parallel relation to the axis of the wall [1. In the opposite ends of the spindle support l8 there are bearings i9 and 2B for supporting a shaft 2 I, the bearing l9 being fixed against axial movement in the support It, and the bearing 28 being mounted in the support l8 so as to have small axial movement to compensate for changes in the length of the shaft or spindle 2| due to temperature changes. A spring 22 is placed so as to bear against the outer race of the bearing 28 so as to accomplish an axial pre-loading of the bearings I 9 and 20, whereby any play in these bearings will be taken up and vibration of the spindle minimized.

On the forward end of the spindle 2|, as best shown in Fig. 2, there is a rotary cutting tool 23, which, in the form of the invention shown for grinding crystals, consists of a disc 24 having a shallow forwardly extending lip 25, which lip 25 carries thereon the cutting element proper 26, which cutting element 26 consists in particles of diamond, or diamond dust, supported in a facing which lies in a plane substantially perpendicular to the axis of rotation of the spindle 2|. The diamond particles constitute cutting teeth which cut, and thereby face, the object or part brought into contact therewith while the cutter 23 is in motion.

The cutter 23 is supported in operative position by being connected to the front face of a hollow body 2'! which is mounted on the front projecting end of the spindle 2!, this hollow body 2? having a shallow concentric boss 28 which fits into an opening 29 in the center of the disc 24, a nut 3t being screwed onto the front threaded end of the spindle 25 to hold the cutter 23 in place against the front wall of the hollow body 21. The disc 24 of the cutter 23 has openings 3| therethrough, inside the flange or lip 25 which communicates with openings 32 in the front wall of the hollow body 21. The rear wall of the hollow body 27 has an annular opening 33 through which the outlet end of a tube 34 is passed so as to conduct cutting, cooling or cleaning liquid into the hollow body, which liquid, due to centrifugal action, passes through the openings 32 and 3! to the front of the disc 24 and then passes outward over the face of the cutting element 26 to continuously wash the same. During the operation of the device, the liquid is constantly fed from the reservoir I! through a conduit 35 which communicates with the pipe or nozzle 34. On the rear end of the spindle 2| there is a pulley 35 connected by belts 31 to a pulley 38 mounted on the shaft of a motor 38a which is secured to the stand l0.

As shown in Fig. 2, the tubular wall i! has therein bearings 39 to support a hollow shaft 40 having a forwardly projecting end 4! on which a work carrier 42 is fixed, which work carrier 42 includes a work holder 43 at its outer end. The shaft 48 is disposed in eccentric relation to the spindle 2i and the work carrier 42 is swingable from the position in which it is shown in Fig. G in centralized relation to a line a-a, to a position in centralized relation to the line b--b,

thereby carrying the work across one side or the annular cutting or grinding element 26 of the cutter 23. A tubular housing 44 is fixed on the rear end of the tubular wall 11, this tubular housing 44 having a counterbore 45 in which a sleeve 41 is turnable, the sleeve 41 having therein a key 48 which engages a keyway 49 in the hollow shaft 40 so that any rotary motion imparted to the sleeve 41 will be transmitted through the key 48 to the shaft 48 on which the work carrier 42 is fixed.

A notch 50 in the lower part of the leftward end of the housing 44, Fig. 2, forms an arcuate slot through which a lever 5| may project from the sleeve 41, the lever 5| being connected to the sleeve 41, as shown in Fig. 4, by means of screws 52. This lever 5| has a slotted extension 5|a engageable by a crank pin 53 carried by a rotating disc 54 whereby swinging movement is given the sleeve 41 so that the sleeve 41 will in turn transmit swinging movement through the key 48 to the shaft 40 to oscillate the work carrier 42. Relative feeding movement of the cutter or tool 23 and the work is accomplished by axial movement of the shaft 40. As shown in Fig. 2, the shaft 40 has within its rightward end a bearing 55 capable of transmitting axial thrust. The inner race of this hearing 55 is fixed on the leftward end of a stem 56 which has a screw 51 projecting rightwardly therefrom. The screw 51 threads through a sleeve nut 58 which normally remains stationary, and is moved only for purpose of adjustment. When the screw 5! is rotated by means of a handle 59, or by the automatic feed mechanism which will be later described, the stem will move axially, and this axial movement will be transmitted by the bearing 55 to the hollow shaft 40, thereby moving the work carrier 42 toward or away from the tool 23, dependent upon the direction of rotation of the screw 51.

The sleeve nut 58 is axially adjustable so that its leftward end, Fig. 2, will serve as a stop to be engaged by a collar 60 positioned between the stem 56 and the screw 51. When the collar 60 comes into engagement with the leftward end of the sleeve nut 58, there can be no further rightward movement of the work carrier 42. The sleeve nut 58 is threaded through a cylindric block Bl which is mounted so that it will project into the rightward end of the tubular housing 44. This block 6|, as shown in Fig. 9, has a tongue or partial flange 62 extending downward therefrom, whereby it may be secured to the rightward end of the housing 44 by means of machine screws 63, Fig. 3, which extend through openings 64 in the wall 62. The external diameter of the block BI is less than the internal diameter of the rightward end of the opening through the housing 44, to accommodate the thin wall 65 of a feed adjusting member 66 which is shown in perspective in Fig. 10.

Surrounding the stem 56 in a position between the rightward end of the shaft 40 and the collar 60 there is a yieldable drive member 61. This drive member 61 includes a cylindric shell 68 having ratchet teeth 69 cut thereon as shown in Fig. 5. This shell 68 is rotatable around the stem 56 and is supported by a, thimble 10 at its rightward end and a radial wall II at its leftward end. Within the shell 68, between the members I0 and H, there are two sets of friction clutch plates, the first set of plates 12 being of tongue and groove connection with the shell 68, and the second set of plates 13 having tongue and groove connection with the-stem 55, there being a spring 14 to press the plates together so that when rotation is imparted to the shell 68, a, rotational force will be carried by the friction clutch formed of the sets of discs 12 and 13 to the stem 56, to accomplish a rotation ofthe screw 5! which will feed the shaft rightward.

A pawl 75, Figs. 2 and 5, is arranged to periodically impart small rotary motion to the shell 68. This pawl 15 is of arcuate form and is swingable in a recess 16 formed in the lower rightward and of the sleeve 41, on a pivot pin 11 which is disposed in parallel relation to the axis of the stem 56. This pawl 15 has an engaging point I8 disposed intermediate its ends for cooperation with the teeth 69 of the shell 58. An arcuate leaf spring, 19, secured to the sleeve 4'! by screws 80, constantly urges the pawl 15 toward engagement with the ratchet consisting of the teeth 63.

When the crank 53, Fig. 3, revolves around the axis of the disc 54, the swinging motion of the lever 5| causes oscillation of the sleeve 47, and since the pawl 15 is mounted on the rightward end of the sleeve 41, it is likewise oscillated around a portion of the leftward end of the shell 58. In one direction of its movement around the axis of the stem 55, the pawl 15 will, through the engagement of its point 18 with the ratchet teeth 69, produce a small rotary movement of the shell 68 around the axis of the stem 55, and if the collar 60, Fig. 2, is out of engagement with the sleeve nut 58, the clutch means embodied with.- in the sleeve 68 will transmit this rotary movement to the stem so that there will be a, slight rightward advance of the screw 51 in the sleeve nut 53. However, the invention provides means for lifting the pawl 15 from engagement with the ratchet teeth 69 during the greater part of its oscillating movement, it being a feature of the invention to permit the pawl '55 to engage the ratchet and move the same only during a relatively short period of time at the end of the return movement of the work carrier All! so that the feeding action of the device will occur just prior to the beginning of the working or forward stroke of the work carrier 42, with the result that a cut will be taken during this working stroke and there will be substantially no cutting action whatsoever during the return stroke of the work carrier 42. This lifting of the pawl 55 is accomplished by the feed adjusting member 65, the cylindric wall 65 of which is notched at its inner or leftward end so as to provide an arcuate wall 8|. At the rightward or outer end of the thin cylindrical wall 65 there is a partial flange 82 which rests against the rightward end of the tubular housing 44 when the wall 65 is inserted into the rightward end of the housing a l as shown in Fig. 2, the arcuate wall ill at the leftward end of the cylindric wall 65 then projecting into the rightward end of the sleeve t? so as to cover a portion of the teeth 69 of the shel1 68. In Fig. 5 the pawl 15 is shown in the position which it assumes at the end of the return stroke of the work carrier 42. stroke of the work carrier 42 occurs, the pawl '15 will move in the direction indicated by the ar row 83, and its chamfered end 84 will engage and ride up over the end 85 of the arouate wall 8|, the pawl 15 being thereby lifted and main tained out of engagement with the ratchet teeth 69 throughout the continuation of the working movement and throughout that portion of the return movement of the work carrier 42, opposite the direction indicated by the arrow 83, required When the working or forward 6 to carry the end 84 of thepawl 15 off of the end 85 of the arcuate wall 8|, at which time the spring 19 will press the pawl 1'5 into engagement with a ratchet tooth, and during the small remaining return movement the pawl 15 will turn the shell 68. By rotating the member 55, the positionof the end 85 of the arcuate wall 8! may be changed, thereby varying the time or distance which the end 84 of the pawl 15 is out of engagement'with the wall BI, and thereby varying the number of ratchet teeth 69 which the pawl 15 will advance; To permit this rotary adjustment of the member 66, its partial flange 82 is provided with an arcuate slot 88 through which a clamping screw 81 is passed. If the member 55 is rotated from the position in which it is shown, in the direction indicated by the arrow 8 3, the rate of feed will be increased. The reverse is true, if the member 56 is rotated in a direction contrary to the arrow 83.

Referring to Fig. 3, the crank pin 53 is shown in full lines in the position it assumes at the end of the return stroke or at the beginning of the working stroke of the work carrier 42. Rotation i of the disc 54 carries the pin 53 downward in clockwise direction from its full line position and the end of the working stroke is reached when the pin 53 arrives at the position in which it is indicated in dotted lines 53a, the working stroke consuming approximately two-thirds of the full circle of rotation of the pin 53 around the center of the disc 54. Therefore the working stroke of the lever 5| and of the work carrier 42 takes substantially twice as long as the return stroke, which is accomplished by clockwise rotation of thepin from its dotted line position 53a to the position in which it is shown in full lines.

As shown in Figs. 2, 6, and 7, the work carrier 42 includes an arm 58 having an opening 89 which communicates with an opening 90in the side wall of the extending portion 4| of the hollow shaft 40. The work holder 43 consists of substantially a quadrant of a cylinder and has an arcuate face 91 which rests in an arcuate seat 92 formed by the curved wall 93 of a member 94 which is secured at the upper arm till. As shown in Fig. 11, the wall 93 has a tongue 95 which enters a companion groove 95 in the member 43 to maintain lateral alignment of the member 43 with the supporting wall 93, and in the wall 93 there is a slot 91, the lower end of which lies above the upper end of the opening 89 so that an arm 98 may be extended from the holder 43 through the slot 97?, the opening 88, and the opening 90 into the interior of the shaft AG, the lower end of: this arm 98 being curved rightwardly as shown in Fig. 7. The lower end of the arm 98 is engaged by adjustment means carried by the shaft 40 for the purpose of rotating the holder 43 around an axis which is substantially parallel to the face of the tool 23. A small roller 99 on the lower end of the arm Hills engaged on one side by a spring pressed member "15 and on. the other side by a pin or rod I!!! which projects leftward through a sleeve 592 which is threaded into the leftward end of the'shaft it. An adjusting ferrule .13 is threaded onto thele-ftward end of the sleeve E02 and is fixed on the outer end 104 of the rod-Hi1, as shown at IE4, so that the axial movement of the member H13 due to its rotation on the threaded portion of the slee e Hi2 will be transmitted to the rod [M to the lower end of the arm 98. The surface of the sleeve and the chamfered end of the ferrule "33 have cooperat- Il ing micrometric' graduations 1'05 and H16 for ref erence by the operator in adjusting the holder 43 through very small angles of rotation. The position of the lower end of the arm 98 is determined by the position of the rod I III against the inner end of which the roller 99 is held by the spring pressed member I00. The work holder 43 is formed so as to receive the Work which may consist of a body I01 in which the crystals I08 are held as shown in Fig. 1. As to an external form, the work body In! is a rectangular prism,.and so as to receive the same, the work holder 43 has faces I09 and III) disposed at right angles so as to provide a V-shaped recess in which the work bodies IIJ'I may be clamped by the simple means which the invention provides. As shown in Fig. 7, a pin I I I extends radially from the work holder 43 through the slot 91 in the arcuate wall 93, and threaded on the outer end of the pin I I I is a nut II2 which compresses a spring I I3 arranged to bear against a friction plate II4 which is in sliding engagement with the outer face of the arcuate wall 93. The work body ID! has trunnions IIlla projecting outwardly of the ends, said trunnions being received in hook-like notches I 01b adjacent the free ends of the side arms IIl'Ic with a substantially U-shaped yoke, indicated generally at IBM. The bottom member IIl'Ie, to which the adjacent ends of arms IIJ'Ic are secured by screws III, is provided with a threaded bore for reception of a screw I079 having an adjusting knob IO'Ih adjacent its outer end. The opposite or inner end of the screw IIlIy engages the adjacent or outer end of the pin III. Each arm IIJIc has a longitudinally extending slot I017 for slldable reception of a pin IIl'Ik fixed in the adjacent end of the work holder 43. Thus the body I01 may be securely held in position in the work holder 43 and the various parts of the assembly are positively retained in their proper position, although permitting angular adjustment.

The disc 54, as shown in Figs. 1 and 3, is fixed on one end of a shaft II5, rotatably carried by a bracket H6 as shown in Fig. 1. As shown in Figs. 1 and 12, a sprocket II! is fixed on the other end of the shaft H5, this sprocket II'I bein driven by a chain II8 which also runs over an idler sprocket H9. The chain H8 is driven by a spiral sprocket I20 carried by a shaft I2I which has on its rearward end, as best shown in Fig. 1, a sheave I22 driven from the motor 38a by a belt I23.

The shaft IZI is supported by a bracket I24 which is swingable around the axis of the shaft H5, so that by swinging of the bracket 124-, the sheave I22 may be moved with relation to the motor shaft so as to tighten the belt I23, without changing the spatial relation of the shafts H and IEI. The idler sprocket H9 is adjustably carried below the drive sprocket I20 by an adjustable arm I25 which is swingable around the axis of the shaft I2I so as to give proper tension to the chain IIB. This adjustable arm I25 has a split ring I26 which surrounds a cylindric boss IE! carried by the bracket I24 in a position surrounding the shaft I2I adjacent the sprocket I20. When a clamping screw I28, Fig. 12, is loosened, the arm I25 may be rotated around the boss I2? until the desired working condition of the belt H8 is reached, after which the screw I23 is again tightened. This arrangement, as indicated by the arrows I30 and I3I of. Fig. '3,- gives the disc 54 a direction of operation opposite to the rotation of the spindle 2!. The direction of rotation of the spindle 2I is the same as that of the motor shaft, but the drive arrangement.

clearly shown in Fig. 12, gives to the disc 54 a rotation opposite to that of the motor. The portion of the cutter or diamond charged cutting element 26 engaged by the work moves downward in view of the direction of rotation of the spindle 2 I, andthe force transmitted from the moving surface of the cutting element 26 to the work tends to move the work downwardly so as to hold it tightly in the work holder.

I claim as my invention:

1. In a device of the character described, the combination of: a rotary tool; means for rotating the tool; shaft means disposed at a side of said tool; an arm supported by said shaft means so that its outer end will swing forth and back across the face of said tool; a work holder adjustably connected to the outer end of said arm, said work holder having a depression to receive a work body; a work body to engage said depression, said body having trunnions projecting from the ends thereof; a yoke extending across the back of said work holder, said yoke having a pair of arms extending across the sides of said holder to engage said trunnions; cam means for moving said yoke so as to tighten said body against said holder; means for adjusting the angular relation of said holder to said tool; means for swinging said arm so that the work carried by said holder will be moved forth and back across the face of said tool; and means for producing a relative feeding movement of said holder and said tool whereby said tool and the work may be moved toward each other.

2. In a device of the character described, the combination of: a rotary tool; means for rotating the tool; shaft means disposed at a side of said tool; an arm suported by said shaft means so; that its outer end will swing forth and back across the face of said tool; a work holder adjustably connected to the outer end of said arm, said work holder having a depression to receive a work body; a work body to engage said depression, said body having trunnions projecting from the ends thereof; a yoke extending across the back of said work holder, said yoke having a pair of arms extending across the sides of said holder to engage said trunnions; cam means for moving said yoke so as to tighten said body against said holder; an adjusting screw means carried by said shaft means; an arm extending from said holder to said adjusting screw means whereby adjusting movement may be transmitted from said adjusting screw means to said holder; a sleeve on said shaft means connected to the screw of said screw means so that it will have movement along said shaft means as said screw means is rotated, there being indications on the surface of said shaft means traversed by said sleeve for showing the adjustment of said holder; means for swinging said arm so that the work carried by said holder will be moved forth and back across the face of said tool; and means for producing a relative feeding movement of said holder and said tool whereby said tool and the work may be moved toward each other.

3. In a device of the character described, the combination of: a rotary tool; means for rotating the tool; shaft means disposed at a side of said tool; an arm supported by said shaft means so that its outer end will swing forth and back across the face of said tool; a work holder at the outer end of said arm, said work holder having a depression to receive a work body; a work body to engage said depression, said body having trunnions projecting from the ends thereof; a yoke extending across the back of said work holder, said yoke having a pair of arms extending across the sides of said holder to engage said trunnions; cam means for moving said yoke so as to tighten said body against said holder; means for swinging said arm so that the work carried by said holder will be moved forth and back across the face of said tool; and means for producing a relative feeding movement of said holder and said tool whereby said tool and the Work may be moved toward each other.

4. In a device of the character described, the combination of: a rotary tool; means for rotating the tool; shaft means disposed at a side of said tool; an arm supported by said shaft means so that its outer end will swing forth and back across the face of said tool; a work holder adjustably connected to the outer end of said arm; means for adjusting the angular relation of said holder to said tool; a lever connected to said arm so as to extend radially from the axis of said shaft means; a crank rotating on an axis parallel to the axis of said shaft means, said crank having sliding connection with said lever whereby rotation of said crank will transmit to said lever and said arm, a fast forward swinging movement during less than half of its full circle of rotation and a slow return movement during the remainder of its circle of rotation; and means for producing a relative feeding movement of said holder and said tool whereby said tool and the work may be moved toward each other.

5. In a device of the character described, the combination of: a rotary tool; means for rotating the tool; shaft means disposed at a side of said tool; an arm supported by said shaft means so that its outer end will swing forth and back across the face of said tool; a work holder adjustably connected to the outer end of said arm; means for adjusting the angular relation of said holder to said tool; a lever connected to said arm so as to extend radially from the axis of said shaft means; a crank rotatable on an axis parallel to the axis of said shaft means, said crank having sliding connection with said lever whereby rotation of said crank will transmit to said lever and said arm a fast forward swinging movement during less than half of its full circle of rotation and a slow return movement during the remainder of its circle of rotation; a drive shaft having driving connection with said rotary tool; a shaft for said crank having a sprocket fixed thereon; an idler disposed in spaced relation to said sprocket; a chain running over said sprocket and said idler; a drive sprocket engaging said chain between said idler and said first named sprocket; means for driving said drive sprocket from said drive shaft; and means for producing a relative feeding movement of said holder and said tool whereby said tool and the work may be moved toward each Other.

6. In a device of the character described, the

combination of: a rotary tool; means for rotating the tool; shaft means disposed at a side of said tool; an arm supported by said shaft means so that its outer end will swing forth and back across the face of said tool; a work holder adjustably connected to the outer end of said arm; means for adjusting the angular relation of said holder to said tool; a lever connected to said arm so as to extend radially from the axis of said shaft means; a crank rotatable on an axis parallel to the axis of said shaft means, said crank having sliding connection with said lever whereby rotation of said crank will transmit to said lever and said arm a fast forward swinging movement durme less than half of its full circle of rotation and a slow return movement during the remainder of its circle of rotation; a drive shaft having driving connection with said rotary tool; a shaft for said crank having a sprocket fixed thereon; an idler disposed in spaced relation to said sprocket; a chain running over said sprocket and said idler; a drive sprocket engaging said chain between said idler and said first named sprocket; and means for driving said drive sprocket from said drive shaft.

FRANK G. VOLKEL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 376,854 Cavert Jan. 24. 1888 457,866 Messaz Aug. 18, 1891 500,561 Carpenter et a1 July 4, 1893 523,504 Armony July 24, 1894 560,249 Gifiord Oct. 23, 1900 901,909 Johnston Oct. 20, 1908 1,121,995 Elvers Dec. 22, 1914 1,230,595 Osterholm June 19, 1917 1,299,717 I-Ialstead Apr. 8, 1919 1,462,653 Osterholm July 24, 1923 1,575,156 Ecaubert Mar. 2, 1926 1,799,763 Raule Apr. 7, 1931 1,920,073 Gorton July 25, 1933 1,929,214 Plantinga Oct. 3, 1933 1,972,160 Osterholm Sept. 4, 1934 2,174,869 Swanson Nov. 14, 1939 2,212,999 Faulder Aug. 27, 1940 2,246,023 Spurling June 17, 1941 2,248,262 Wilhide July 8, 1941 2,269,946 Lange Jan. 13, 1942 2,286,886 Anderson June 16, 1942 2,294,872 Wood Sept. 1, 1942 2,324,266 Muskovin et a1 July 13, 1943 2,380,332 Scheer July 10, 1945 2,383,131 Kirsch Aug. 21, 1945 2,393,727 Alber Jan. 29, 1946 2,404,282 Fruth July 16, 1946 2,429,464 Jearum Oct. 21, 1947 Certificate of Correction Patent No. 2,509,402 May 30, 1950 FRANK G. VOLKEL It is hereby certified that errors appear in the printed specification of the above numbered patent requiring correction as follows:

Column 8, line 37, for suported read supported; column 10, line 37 list of references cited, for Armony read Armeny; line 38, for the patent number 560,249 read 660,249; line 49, for 2,174,869 read 2,179,869; line 59, for Alber read.- Aber;

and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Ofiice.

Signed and sealed this 19th day of September, A. D. 1950.

[SEAL] THOMAS F. MURPHY,

Assistant Gammz'ssz'oner of Patents. 

